[EN] The synthesis of capped mesoporous silica nanoparticles (MSN)
conjugated with an antibody (AB) as a gatekeeper has been
carried out in order to obtain a delivery system able to release
an entrapped cargo (dye) in ...[+]

[EN] The synthesis of capped mesoporous silica nanoparticles (MSN)
conjugated with an antibody (AB) as a gatekeeper has been
carried out in order to obtain a delivery system able to release
an entrapped cargo (dye) in the presence of a target molecule
(antigen) to which the conjugated antibody binds selectively.
In particular, MSN loaded with rhodamine B and functionalized
on the external surface with a suitable derivative of N-(t-butyl)-
3-oxo-(5a,17b)-4-aza-androst-1-ene-17-carboxamide (finasteride) have been prepared (S1). The addition of polyclonal antibodies against finasteride induced capping of the pores due to
the interaction with the anchored hapten-like finasteride derivative to give a MSN¿hapten¿AB nanoparticle S1-AB. It was
found that the addition of capped material S1-AB to water solutions containing finasteride resulted in displacement of the
antibody, pore uncapping and entrapped-dye release. The response of the gated material is highly selective, and only finasteride, among other steroids, was able to induce a significant
uncapping process. Compared with finasteride, the finasteride
metabolite was able to release 17% of the dye, whereas the exogen steroids testosterone, metenolone and 16-b-hydroxystanozolol only induced very little release of rhodamine B
(lower than 10%) from aqueous suspensions containing sensing solid S1-AB. A detection limit as low as 20 ppb was found
for the fluorimetric detection of finasteride. In order to evaluate a possible application of the material for label-free detection of finasteride, the capped material was isolated and
stored to give final sensing solid S1-AB-i. It was found to display a similar behavior towards finasteride as to that shown by
freshly prepared S1-AB; even after a period of two months, no
significant loss of selectivity or sensitivity was noted. Moreover,
to study the application for the detection of finasteride in biological samples, this ¿aged¿ material, S1-AB-i, was tested using
commercially available blank urine as matrix. Samples containing 70 and 90% blank urine were spiked with a defined
amount of finasteride, and the concentration was determined
using capped S1-AB-i. Recovery ranges from 94% to 118%
were reached.[-]

Financial support from the Spanish Government (project MAT2009-14564-C04-01) and the Generalitat Valenciana (Spain) (projects PROMETEO/2009/016 and PROMETEO/2010/008) is gratefully acknowledged. E. C. thanks the Minesterio ...[+]

Financial support from the Spanish Government (project MAT2009-14564-C04-01) and the Generalitat Valenciana (Spain) (projects PROMETEO/2009/016 and PROMETEO/2010/008) is gratefully acknowledged. E. C. thanks the Minesterio de Ciencia e Innovacion (MICINN, Spain) for her fellowship.[-]